Ultrasonication increases γ‐aminobutyric acid accumulation in coffee leaves and affects total phenolic content and angiotensin‐converting enzyme inhibitory activity

Abstract

In this study, the accumulation of γ-aminobutyric acid (GABA) in coffee leaves under ultrasonication and the impacts on total phenolic content (TPC), the activities of glutamate decarboxylase (GAD) and GABA transaminase (GABA-T), and angiotensinconverting enzyme (ACE) were investigated. The pH, incubation time, and ultrasonic power were the three most important factors that affected the accumulation of GABA. Coffee leaves treated with 20/40 kHz ultrasound have the highest GABA and the greatest GAD and ACE inhibitory activity. After optimization with a Box-Behnken design, GABA content was increased by 1.6 times under the optimal conditions of pH 5.9, incubation time 6.6 hr, and ultrasonic power 150 W. Our study indicated that ultrasonication activated GAD while inhibited GABA-T, thereby leading to an increase in GABA and ACE inhibitory activity. Ultrasonication also enhanced TPC; however, long time incubation caused the oxidation of phenolic compounds, and thus, affected the ACE inhibitory activity.Novelty impact statement: This is the first research that studied the enrichment of Gamma-aminobutyric acid (GABA) in coffee leaves using ultrasound stress. GABAenriched coffee leaves can be used to prepare tea-like beverage or natural health products to prevent hypertension, anxiety, and sleeplessness.

Zinc oxide nanoparticles synthesized using coffee leaf extract assisted with ultrasound as nanocarriers for mangiferin

“…All the ultrasound treatments were performed in a multi-frequency power ultrasound device designed by Dr. Haile Ma's group (Jiangsu University) ( Ji et al, 2021 ). The effects of pH (7.0, 7.5, 8.0, 8.5, 9.0), mass ratio of coffee leaves to C 4 H 6 O 4 Zn•2H 2 O (0.23, 0.46, 0.68, 0.91, 1.14, 1.37, 1.71, 2.28), ultrasound time (10, 20, 30, 40, 50 min), ultrasound frequency (single-frequency (20, 28, 40 kHz), dual-frequency (20/28, 20/40, 28/40 kHz) and triple-frequency (20/28/40 kHz), ultrasound power (60, 120, 180, 240, 300 W) and temperature (20, 25, 30, 40, 50, 60, 70 °C) on the yield of ZnO NPs were investigated using one factor at a time experimental design.…”

Recent advances of γ-aminobutyric acid: Physiological and immunity function, enrichment, and metabolic pathway

“…Additionally, downregulated expression of GABA-T in rice by RNAi promoted the accumulation of GABA in rice ( 119 ). After the ultrasonic treatment, the expression of the gad gene in fresh coffee leaves was activated by, inhibiting the GABA-T activity, and increasing GABA content ( 120 , 121 ). GABA-T enzyme has two isomers which are pyruvate-dependent GABA-T (GABA-TP) and α-ketoglutarate-dependent GABA-T (GABA-TK).…”

Proposing Signaling Molecules as Key Optimization Targets for Intensifying the Phytochemical Biosynthesis Induced by Emerging Nonthermal Stress Pretreatments of Plant-Based Foods: A Focus on γ-Aminobutyric Acid

“…64 In coffee leaves, US treatments increased the accumulation of GABA up to 60% higher than the untreated samples, with accompanied increase of total phenolic contents, among which the process parameters including pH, incubation time, and ultrasonic power were identified as the most relevant. 65 It was noted in these studies that the increase in GABA and phenolic compounds such as isoflavone and flavonoid tends to be interconnected, inferring that the GABA shunt could be metabolically coupled with other major pathways in secondary metabolism (e.g., shikimic acid pathway and phenylpropanoid pathway). In fact, in response to traditional stress factors, the enhanced synthesis of phenolics and GABA has been reported in multiple cases.…”

“…To investigate the effects of different combination modes on the accumulation of GABA, US treatments were performed at 66 h during a 72 h germination of red rice or applied prior to germination, observing that GABA contents were significantly higher than the germinated grains without US pretreatments, while there was no significant difference in the two combination modes between US and germination . In coffee leaves, US treatments increased the accumulation of GABA up to 60% higher than the untreated samples, with accompanied increase of total phenolic contents, among which the process parameters including pH, incubation time, and ultrasonic power were identified as the most relevant . It was noted in these studies that the increase in GABA and phenolic compounds such as isoflavone and flavonoid tends to be interconnected, inferring that the GABA shunt could be metabolically coupled with other major pathways in secondary metabolism (e.g., shikimic acid pathway and phenylpropanoid pathway).…”